The EXT_shader_texture_lod extension is part of the WebGL API and adds additional texture functions to the OpenGL ES Shading Language which provide the shader writer with explicit control of LOD (Level of detail).
The WEBGL_compressed_texture_atc extension is part of the WebGL API and exposes 3 ATC compressed texture formats. ATC is a proprietary compression algorithm for compressing textures on handheld devices.